DC-DC converting controller

A DC-DC converting controller coupled to an output stage and an external resistor network and providing a pulse-width-modulation (PWM) signal to control the output stage to provide an output voltage is disclosed. The DC-DC converting controller includes a sensing circuit, a droop current circuit, a first pin and a PWM signal control loop. The sensing circuit, coupled to the output stage, provides a sensing current. The droop current circuit, coupled to the sensing circuit, provides a droop current according to the sensing current. The first pin, coupled to the droop current circuit and external resistor network, provides the droop current to make the external resistor network provide a second reference voltage. The PWM signal control loop, coupled to the external resistor network, generates a PWM signal according to the output voltage and the second reference voltage. The droop current is reduced to a default value with a default time.